1. Field of the Invention
The present invention relates to a manufacturing device and a manufacturing method for an optical disc, which can prevent involving bubbles while forming a protective film on a disc substrate or while forming an adhesive layer between disc substrates.
2. Description of the Related Art
In a conventional manufacturing method of an optical disc, when a protective film is formed on a surface of a disc substrate as an optical transparent layer, or when a adhesive layer is formed on one of or both of disc substrates in order to bond two or more of the disc substrates, a center hole of the disc substrate is closed by a capping member, and a liquid material is supplied onto the capping member. Thereafter, the liquid material uniformly outspreads over the entire surface of the disc substrate by a spin-coating method in a high-speed rotation.
FIGS. 6A to 6C show a prior art. As shown in FIG. 6A, a reversely protruding portion 43a of a capping member 43 is fitted into a dented portion 42d formed in a pin-shaped member 42c of a disc-supporting base 42 having a disc substrate 11 mounted thereon. Furthermore, the reversely protruding portion 43a is fixed into the dented portion 42d by vacuuming an inside of a vacuuming hole 42a, and thereby closing a center hole 11a of the disc substrate 11. In this construction in which: the reversely protruding portion 43a of the capping member 43 is fitted into the dented portion 42d of the pin-shaped member 42c; and furthermore, a back side of the capping member 43 is supported by a top of the pin-shaped member 42c, the capping member 43 is fixed to the pin-shaped member 42c regardless of the shape of the disc substrate 11, and thereby making it difficult to fittingly and completely attach the capping member 43 onto the disc substrate 11. For example, FIG. 6A shows a case in which there is an non-contacting portion 300 between the right side of the capping member 43 on the drawing and the disc substrate 11 (i.e., FIG. 6A shows the case where a partial gap is formed between the capping member 43 and the disc substrate 11. Moreover, the reference symbol 42b denotes absorption holes formed in the disc-supporting base 42 in order to perform a vacuum-absorption of the disc substrate 11.
Next, as shown in FIGS. 6B and 6C, liquid material 200 is supplied from a liquid supplying nozzle 100 so as to form a ring surrounding a center of the capping member 43, and the disc substrate 11 is rotated in a high-speed to spread the liquid material 200 over the disc substrate 11 using a centrifugal force. At this time, if the disc substrate 11 is rotated while having the minor gap between the disc substrate 11 and the capping member 43, there is a problem in that the liquid material 200 enters into the gap and thereby causing high possibility of involving bubbles therein. The bubbles involved in the liquid material 200 are suffered from the centrifugal force while spreading the liquid material 200 in the high-speed rotation, and move from the inward to the outward. Thus, if the liquid material 200 covering an information recording area involves the bubbles, such bubbles will cause errors in writing and reading information. In addition, even when the capping member 43 is removed after spreading the liquid material 200 while having the minor gap between the disc substrate 11 and the capping member 43, there are high possibility of swallowing the liquid material 200 into the gap and thereby generating the bubbles, or of mixing with the liquid material 200 already entered in the gap and thereby generating the bubbles.
In addition, since the disc substrate 11 is held by the vacuum adsorption on the disc-supporting base 42, the liquid material 200 is drawn and easily enters into the gap between the capping member 43 and the disc substrate 11 through a gap between the center hole 11a of the disc substrate 11 and the pin-shaped member 42c. Furthermore, even in the case in which the capping member 43 is held by a vacuum adsorption on the pin-shaped member 42c, the liquid material 200 is drawn and easily enters into the gap between the disc substrate 11 and the capping member 43. As mentioned in the above, the bubbles on the disc substrate 11 will cause problems in the quality and the appearance of the disc substrate 11.
Therefore, the numbers of countermeasures are proposed for a method of improving the contact between the capping member and the disc substrate. For example, there is a proposed a construction in which: a space is formed between the capping member and the pin-shaped member; and making the space into a vacuumed state through a vacuuming device connected to a vacuuming path, and thereby pressing down the capping member to fittingly fix it onto the disc substrate (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2002-316084, Japanese Unexamined Patent Application, First Publication No. 2005-353282, and Japanese Unexamined Patent Application, First Publication No. 2006-59454).
The contact between the disc substrate and the capping member is significantly influenced by the processing accuracies of the disc substrate, the capping member, and the like. In the above-mentioned conventional art, the capping member can be pressed down to only one direction which is substantially vertical to the disc substrate, by a vacuum adsorption or other attracting mechanisms. In order to completely seal the around of the center hole of the disc substrate with the capping member, it was necessary to strongly press the capping member onto the disc substrate. However, even when the capping member is strongly pressed, it was still difficult to completely close the center hole. In addition, increasing the pressing force onto the disc substrate may cause deformations and curbing thereof, and thereby influences on the quality. In this construction, there is a case in which the pressing force onto the disc substrate partially increases. In such a case, the problems of causing the deformations and the curving of the disc substrate become severe.
In view of the above-mentioned circumstances, the present invention has an object of providing a manufacturing device and a manufacturing method for an optical disc, which can increase the contact between a disc substrate and a capping member, and thereby suppressing involving bubbles into liquid material.